Such watch cases are well known. In the existing products, the hollowing-out of the solid portions of the caseband is obtained by machining from the recess intended to receive the horological movement, the hollow portions thus produced being concealed by the casing ring, secured on the caseband and supporting the movement.
The saving in weight of precious metal is, as well understood, that much greater as the hollow is deep. However, the more substantial the hollow, the more the wall of the caseband becomes thin and the case fragile, principally in respect of shocks to the outer face and stresses, often substantial, appearing for example at the winding stem passage and the horns.
In order that the case maintain sufficient strength, reinforcement pieces are welded onto critical locations and the horns do not include any hollowing-out.
Now, according to the law, (Swiss Federal Law 941.31, Jun. 20, 1933) every piece added to a watch case of noble metal must also be of noble metal if it is secured permanently onto the case, or be readily separable from the case without special tools should the piece be of a base metal or base metal alloy.
Under these conditions, given that the reinforcement pieces are welded onto the caseband, they must likewise be of noble metal. This constitutes an important drawback since these pieces increase the weight of the case and the securing thereof, its manufacturing cost. The necessity of maintaining massive horns constitutes another drawback since the weight of the horns represents a substantial portion of the overall weight of the case.
The purpose of the invention is to propose a watch case of noble metal not showing these drawbacks.